But yes, we put a TON of work into this and we have never received a penny of income until last week (even ended up paying the income tax out of our own pockets) so it's time to collect on the work!

Turnkey operators don't work like that and they are more like a broker collecting a fee for their work (regardless of the long-term performance).

That way, you could live in one, purchase with little down since you can use a primary residence loan with a low down payment, and collect rental income on the other 3 units.

Let her know you'll send her to collections if she refuses. 

To avoid opening a bank account and following all the rules that come with collecting and holding a security deposit I figured id just treat last months rent as security deposit.

What’s the legal way to collect payments from roommates that live with me in the same house? 

The LLC collects rent, pays expenses, and distributes funds to the owners based on your partnership agreement.

It's completely legal that's what I do I pay the bills to the utility company and send a copy to the tenants and collect the 60/40 split from them each month

They now collect that informaton at the birthing hospital. 

I'd also suspect that as an owner-occupant, one might be able to skirt strict STR laws, and rent out a primary in an extremely in-demand market, especially in the near-term (think collecting huge fees seasonally around CU football games the next few years).